The present invention relates to a variable displacement swash plate type compressor, in which pistons engaged with a swash plate are reciprocated by a stroke corresponding to the inclination angle of a swash plate.
Such a compressor is disclosed in Japanese Laid-Open Patent Publication No. 1-190972. The compressor has a housing that accommodates a swash plate and a movable body, which is coupled to the swash plate to alter the inclination angle of the swash plate. A control pressure chamber is formed in the housing. As control gas is introduced to the control pressure chamber, the pressure inside the control pressure chamber is changed. This moves the movable body along the axis of the rotary shaft. As the movable body is moved along the axis of the rotary shaft, the inclination angle of the swash plate is changed.
Specifically, when the pressure in the control pressure chamber is increased, the movable body is moved toward a first end in the axial direction of the rotary shaft. The movement of the movable body increases the inclination angle of the swash plate. When the pressure in the control pressure chamber is lowered, the movable body is moved toward a second end in the axial direction of the rotary shaft. The movement of the movable body decreases the inclination angle of the swash plate. As the inclination angle of the swash plate is reduced, the stroke of the pistons is reduced. Accordingly, the displacement is decreased. In contrast, as the inclination angle of the swash plate is increased, the stroke of the pistons is increased. Accordingly, the displacement is increased. The variable displacement swash plate type compressor has a displacement control valve, which controls the pressure in the control pressure chamber.
In such a variable displacement swash plate type compressor, when the switch of the vehicle air conditioner is turned off and the current supply to the electromagnetic solenoid of the displacement control valve is stopped, changes in the pressure in the suction pressure zone may maintain the inclination angle of the swash plate at an angle greater than the minimum inclination angle. When the air conditioner switch is turned on again and the current supply to the electromagnetic solenoid is resumed, the displacement is abruptly increased. This increases the load on the variable displacement swash plate type compressor. Therefore, the inclination angle of the swash plate is preferably minimized when the air conditioner switch is turned off and the current supply to the electromagnetic solenoid is stopped.